February 10, 2020
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No IQ benefit with levothyroxine in pediatric subclinical hypothyroidism

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Mariacarolina Salerno

Children with mild and persistent untreated subclinical hypothyroidism did not have impaired neurocognitive function and did not see neurocognitive benefits from 2 years of levothyroxine therapy, according to findings from a case-control study reported in The Journal of Clinical Endocrinology & Metabolism.

“The findings of this study further support the current practice to not routinely recommend levothyroxine therapy in all children with serum thyroid-stimulating hormone values below 10 mIU/L,” Mariacarolina Salerno, MD, PhD, associate professor of pediatrics and head of the pediatric endocrinology unit in the department of translational medical sciences at the University of Naples, Italy, told Healio. “Additional controlled randomized studies are needed to definitively establish the effects of subclinical hypothyroidism and levothyroxine treatment on neurocognitive function.”

Salerno and colleagues analyzed data from 34 children with long-lasting, idiopathic and mild subclinical hypothyroidism and 34 healthy, matched controls (mean age, 9 years; 18 boys). Among children with subclinical hypothyroidism, 20 underwent 2 years of levothyroxine treatment (treatment group; starting dose, 50 µg per day) and 14 who declined treatment were reassessed after 2-years of follow-up (observation group). Researchers evaluated IQ and specific cognitive domains for all children at baseline and at 2 years. Researchers used multiple regression analysis to test the effects of changes in TSH levels after treatment on intellectual outcome, using change in TSH as a predictor and neurocognitive parameters as dependent variables.

At baseline, children with subclinical hypothyroidism had IQ scores that were normal and comparable with controls for the full-scale (mean, 100.4 vs. 101.8), verbal (mean, 99.7 vs. 98.3), and performance domains (mean, 101.2 vs. 105).

brain 
Children with mild and persistent untreated subclinical hypothyroidism did not have impaired neurocognitive function and did not see neurocognitive benefits from 2 years of levothyroxine therapy.
Source: Shutterstock

At 2 years, children in the levothyroxine treatment group experienced TSH normalization, decreasing from a mean of 6.3 mIU/L at baseline to 2.84 mIU/L at 2 years (P < .0001). However, levothyroxine therapy was not associated with a change in IQ scores or in verbal or performance subtest scores. Additionally, researchers observed no differences in IQ scores at 2 years for treated children compared with untreated children with subclinical hypothyroidism.

“This study provides evidence that neurocognitive function in children is not impaired by mild and persistent untreated idiopathic subclinical hypothyroidism and does not benefit from 2 years of levothyroxine supplementation,” the researchers wrote. “These findings have relevant clinical implications and further support the current practice to not routinely recommend levothyroxine therapy in all children with serum TSH values below 10 mIU/L.”

Salerno said children with subclinical hypothyroidism should be monitored for hypothyroidism based on clinical symptoms and laboratory assessment of thyroid function.

“For now, the decision to initiate therapy should be based on consideration of individual factors and clinical judgement,” Salerno said. – by Regina Schaffer

For more information:

Mariacarolina Salerno, MD, PhD, can be reached at the Pediatric Endocrinology Unit, Department of Translational Sciences, University “Federico II” of Naples, Via S. Pansini, 5, 80131, Naples, Italy; email: salerno@unina.it.

Disclosures: The authors report no relevant financial disclosures.